﻿<p>
An element component is a representation for minor items included in, added to or connecting to or between
   elements, which usually are not of interest from the overall building structure viewpoint.
   However, these small parts may have vital and load carrying functions within the construction.
   These items do not provide any actual space boundaries.
   Typical examples of <em>IfcElementComponent</em>s include different kinds of fasteners and various accessories.
</p>

<p>One or several instances of subtypes of <em>IfcElementComponent</em> should always be accompanied by a defining instance of a respective subtype of <em>IfcElementComponentType</em>.  The type object holds shape and material information.</p>


<blockquote class="history">HISTORY&nbsp; New entity in IFC2x2</blockquote>

<p>It is often desirable to model a number of same-shaped element components by means of a single
occurrence object, e.g. several bolts within a connection or a row of reinforcement elements.
In this IFC release, this is possible by means of multiple mapped representation as documented below.</p>

<p>To express the multiplicity of element components also on a higher semantic level,
a <em>Qto_ElementComponentPatternQuantities</em> should be provided via <em>IfcRelDefinesByProperties</em>
and contain the number of pieces which are placed by a single <em>IfcElementComponent</em> instance.</p>

<p class="use-head"><b>Symbolic Representation</b></p>

<p>A symbolic representation is defined for a row of components or several rows of
components within a single instance of <em>IfcElementComponent</em>.  Such rows or arrays may
contain possibly large numbers of individual pieces.  The product definition shape consists of
an <em>IfcShapeRepresentation</em> with the attribute values</p>
<ul>
  <li><em>RepresentationIdentifier</em> : 'Row'</li>
  <li><em>RepresentationType</em> : 'GeometricCurveSet'</li>
</ul>
<p>and one or several curves as geometric items.  The curves represent where reference points of
the pieces are located.  For example, such reference points may be at the heads of mechanical fasteners
or at the starting point of the extrusion axis of reinforcement bars.  In case of straight components
(bolts, nails, staples, straight reinforcement bars, or similar), the local placement of the
<em>IfcElementComponent</em> shall be located and oriented such that the local z axis is parallel with
the axes of the components.  A <em>Qto_ElementComponentPatternQuantities</em> should denote the count
of pieces in the row or array and their spacing.</p>
